What structure is the faintly visible, tubular-shaped, soft tissue opacity visible in the caudal portion of the thorax, ventral to the aorta, and dorsal to the caudal vena cava?
What structure is the faintly visible, tubular-shaped, soft tissue opacity visible in the caudal portion of the thorax, ventral to the aorta, and dorsal to the caudal vena cava?